A small, focused desktop app that merges split stream recordings into one file using ffmpeg stream-copy (-c copy, no re-encoding — fast and lossless). Built with Tauri 2 (Rust backend + TypeScript UI).

This is a standalone spin-off of Stream Studio with the song-detection feature removed, so it needs no Python and no ML model — just ffmpeg.

Features

Drag-and-drop / browse to add videos, reorder, select which to merge.
Stream-copy concat with honest real-time progress. On local NVMe a merge runs at ~95 % of plain file-copy speed — the disk is the limit, not the app.
History tab: every merge (done, failed, stopped, or interrupted by a crash) with its files, size, time and MB/s. Show the output in its folder, or load the same files again with "Merge again".
BiliBili-Live filename helper ([date][uploader][title] → readable name).
Optionally delete the originals after a successful merge.
Optional Web-optimize MP4 (+faststart), off by default. It moves the MP4 index to the front so playback can begin mid-download, but ffmpeg has to re-read and re-write the whole file to do it — measured at 17–56 % extra time locally and 60 % over a NAS. Local players don't need it.

Portable: everything stays in one folder

Nothing is written outside the app folder — not to %APPDATA%, not to the registry. Copy the folder to another PC and history, theme and options come with it:

VideoConcat\
  Video Concat.exe
  ffmpeg.exe, ffprobe.exe
  data\
    history.jsonl   <- merge history, one JSON line per job
    running.json    <- only while a merge runs; left behind = "interrupted"
    webview\        <- WebView2 profile (theme, options)

data\ is created on first run. If the folder isn't writable (say, under Program Files), the app still works but shows a banner and keeps no history. It needs the WebView2 runtime, which ships with Windows 10 and 11.

Build a standalone (copy-paste) version

Double-click build.bat. It compiles the app and assembles a portable folder with ffmpeg bundled:

dist-portable\VideoConcat\
  Video Concat.exe   <- double-click this
  ffmpeg.exe         <- bundled
  ffprobe.exe        <- bundled

Copy that whole VideoConcat folder to any Windows PC and run it — nothing else to install. To upgrade an existing copy, replace only Video Concat.exe and keep its data\ folder; history carries over.

Build requirements (on the build machine only)

Node.js
Rust (winget install Rustlang.Rustup)
Visual Studio 2022 with the Desktop development with C++ workload
ffmpeg: in C:\ffmpeg\bin, on PATH, or point FFMPEG_DIR at any folder holding ffmpeg.exe + ffprobe.exe (an existing portable copy works: set FFMPEG_DIR=%USERPROFILE%\Documents\VideoConcat)

Building from a network share is slow and fragile (thousands of small files in node_modules and target). Copy the source to a local disk first.

Develop

Double-click dev.bat (hot-reload UI + Rust). Needs ffmpeg on PATH. In dev mode the data\ folder sits next to the debug exe in src-tauri\target\debug\.

Test

npm run build            # the Rust tests embed dist/, so build the UI first
cd src-tauri && cargo test

Covers the BiliBili rename parser, concat-list path escaping (\\?\ and UNC prefixes, quotes), duration reuse, "never delete the output", and history crash recovery.

Benchmark

tools/bench_concat.py times each pipeline stage with the exact ffmpeg flags the app uses, against the I/O floor of a plain file copy:

python tools/bench_concat.py --ffmpeg-dir <folder with ffmpeg> --make 6 --src D:\bench --dst D:\bench\out

Icons

The app icon lives as vector art in src-tauri/icons/icon.svg — a rounded-square gradient tile with the three-filmstrips-into-one-arrow mark. Everything else in src-tauri/icons/ is generated from it:

python tools/make_icons.py

That rewrites the PNGs and icon.ico with 8x supersampling and a real alpha channel, dropping sub-pixel detail (sprocket holes below 48px, the play-triangle knockout below 64px) rather than smearing it. Only the Windows/desktop icons are regenerated; the android/ and ios/ subfolders are untouched.

To fix the icon on an already-built exe without recompiling it:

python tools/patch_exe_icon.py "path\to\Video Concat.exe"

That rewrites only the RT_ICON / RT_GROUP_ICON resources — .text, .rdata and .data come out byte-identical — and keeps a .bak alongside. Explorer caches icons aggressively, so follow it with ie4uinit.exe -show.

Both tools need pillow and numpy.

README.md Unescape Escape

Video Concat